Best Birthday Ever
by Rusher4lifeBTR4
Summary: It's a very special day in apartment 2J. Katie, everyone's favourite little devil has turned 11, and this certainly can't go uncelebrated. Kendall and Katie sibling fic.


"Guys..." Kendall whispered. It was early, only 6 in the morning, yet he was wide awake for one special reason: today was Katie's 11th birthday.

Getting no response at all, Kendall repeated himself, this time a bit louder.

"Guys."

James, Carlos and Logan groaned but refused to even just slightly move.

"GUYS!"

Kendall watched with a grin as his three best friends let out girlishly high squeaks, tumbling off their beds in fright.

"Dude... what?" James asked moodily, rubbing the back of his head, which he had hit on the ground in the process of falling. He glanced at the clock on the wall: it was 6 in the morning. He gave Kendall the mother of death glares. "You ruined my beauty sleep!"

Kendall rolled his eyes and snickered.

"All of you, get your butts out of bed and get dressed! It's Katie's birthday!"

The other three boys immediately jumped up, now excited. They have been secretly planning Katie's birthday the whole week. It wasn't an easy job to keep a secret from Katie Knight: the little girl, though very small and cute, was capable of finding out about anything, literally ANYTHING through her sly ways. Though this time she wasn't expecting anything special to happen.

The newly 11-year-old Katie, was now sleeping soundly in her room. She looked like a tiny burrito, curled up under the covers and snoring lightly. A tiny, snoring burrito.

Just 30 minutes later, Kendall and his friends quietly opened her bedroom door. The smell of freshly baked pancakes filled the house that Logan had just made, specifically for the birthday girl. Very quietly, they decorated her room with balloons, careful not to wake her. Each of the guys had a small present in their hands: Kendall had a teddy bear, James a fancy hairbrush, Carlos a purple helmet and Logan a book. The guys looked at each other and nodded.

Kendall carefully sat on the side of Katie's bed and leaned over her with a smile, gently rubbing her back.

"Hey Baby Sis... good morning." He whispered. Katie groaned, rolling onto her other side. The guys chuckled lightly.

"Come on, Katie." Kendall laughed, shaking her shoulder lightly. "Time to get up."

"Nooo." The little girl rolled onto her stomach, pulling the covers over her head. "Go away!" She demanded.

The guys exchanged mischievious glances, then nodded. Putting the gifts down, they all gathered next to the bed and towered over Katie.

"One..." Kendall mouthed. "Two... Three." The boys started tickling her.

"Stooop!" The little girl erupted into giggles, shrieking with laughter as she tried to get out from under the covers. The guys chuckled right along with her. She was wide awake.

"Guys!" She gasped, laughing non-stop as she finally managed to climb out from under the covers. She let out a scream of giggles as Kendall grabbed her and lifted her onto his lap, trapping her in his arms.

"Alright, that's enough." Kendall told his friends, making them back off. Katie was still shivering with laughter, leaning against her big brother.

"You ready, Baby Sis?" Kendall asked with a smile. Katie looked up at him with a confused frown.

"Ready for what?"

The guys looked at each other. James tapped his foot three, times, then they all started singing.

"Happy birthday to you, happy birthday to you..."

Katie smiled, looking up at her four brothers. Even though she mostly referred to them as "the idiots", she had to admit, they sometimes had pretty good moments, kind of like these. She giggled and buried her face in Kendall's shoulder, smiling as she felt him kissing her cheek.

"... happy birthday too youuuuu!" The guys started hooting and clapping as Kendall picked Katie up and twirled her around in the air at the last verse, then sat her on his hip. It's been quite a while since she was picked up but she didn't mind. She beamed as she gave all the guys a half hug, holding onto Kendall's neck still. Finally, she threw her hands around her brother, grinning happily as he rubbed her back.

"Now Katie." Kendall said as he gently lowered his sister onto her bed. "It's time for your first gifts of the day."

Between happy squeaks and another few rounds of hugs, Katie recieved her teddy bear, the hairbrush, the helmet and the book.

"Thank you guys so much!" She said for the 100th time this morning. The boys smiled and headed for the door.

"Get dressed, Little Sis. We have a long day ahead of us." Kendall smiled mysteriously.

"Where are we going?" Katie bounced on her bed excitedly. Her brother just winked.

"You'll see."

Leaving a happy Katie behind him, Kendall left her room as well and looked around in the living room. Logan was still busy preparing Katie's breakfast, Carlos was scrubbing his helmet and James was staring at himself in the mirror, loudly complimenting his reflection. Kendall rolled his eyes and turned around, pulling an envelope out of his pocket, opening it. Finally, the day has come. He grinned evilly as he read it over again.

 **~ Flashback ~**

Five-year-old Katie was sitting in the living room with her brother, who was doing his homework. The little girl was quietly drawing, just letting her thoughts flow. Then, suddenly, she lifted her head.

"Kendall?" She asked.

"Mmm?" Her brother murmered, not looking up from his books.

"What's a birthday spanking?"

Frowning, Kendall put his book down. Katie was looking at him with a curious expression, eyes wide.

"Why do you wanna know, Baby Sis?" He smiled lightly.

Katie shrugged, continuing to draw.

"One of the boys in kindergarten, Tommy said that he got a birthday spanking from his mommy at his birthday party. I thought it was a rude present."

11-year-old Kendall chuckled lightly.

"Birthday spankings are a tradition in some families, Katie. The birthday boy or girl gets the same number of spanks as their age, and sometimes one to grow on. The spanks aren't supposed to hurt though, they're just for fun."

Katie giggled at the thought.

"I still wouldn't want a spanking on my birthday."

"Are you sure?" Kendall teased, completely abandoning his homework and walking up to Katie. "It's your birthday in a few days." He reached out and tickled his little sister's sides, making her squeal and giggle as she rolled back and forth, trying to push Kendall's hands away.

"Stop!" She laughed, letting out a relieved sigh as Kendall pulled his hands back and plopped down next to her. They stayed quiet for a bit before Kendall spoke up.

"What is one thing you wanna accomplish by the time you're six?"

If others heard this, they probably would've said this is too deep of a question for a 5-year old. Katie, of course, wasn't just an average 5-year-old. She was the smartest little girl Kendall had ever known.

"I wanna become an astronaut!" Katie exclaimed, grinning happily, then she turned to Kendall. "Did you manage to accomplish the things you wanted by the time you turned eleven?"

Kendall pursed his lips together, shaking his head.

"Nope, I'm still not a hockey champion."

There was another pause. This time it was Katie's turn to break the silence.

"I'm gonna have a boyfriend by the time I'm eleven."

"No way!" Kendall protested, his overprotective big brother instincts immediately kicking in. "You think I'm gonna let you?"

"Yes." Katie giggled. "Just watch. I'm gonna have a boyfriend by then."

Kendall shook his head, snorting.

"Not on my watch."

An idea popped into Katie's mind as she sit up straight. At the age of five, Katie just learned what bets are and she was all about them.

"Wanna make a bet?" She offered, grinning mischeviously. Kendall chuckled but nodded.

"Fine. What's the deal?"

"If I'm still single by the age of eleven, I get a birthday spanking on my eleventh birthday."

Kendall grinned.

"Are you that confident in yourself?"

The tiny girl scrunched her nose up, smiling.

"Yes, I am."

"Alright." Kendall laughed, extending his hand. Katie firmly shook it. "But, to make sure you don't forget, I wanna have this on paper. Take a pencil and write what I say. I, Katherine Alexa Knight..."

The vow was simple and short, signed by Katie at the bottom. Kendall folded it and put it in an envelope, hiding it in a box under his bed. He knew the time would once come.

 **~ End of flashback ~**

And the day has come. Kendall had to admit, seeing Katie grow up was harder than he expected. Still, it was the most beautiful process he ever got to experience. His heart was full of love for his baby sister, and after quickly shoving the envelope back into his pocket, he couldn't help but pulled Katie into another hug as she entered the living room, fully dressed.

"Oooh, breakfast!" Katie exclaimed, pushing her brother away and rushing to the table. Kendall watched her with a smile, thinking about all the fun they were gonna have today. Their first stop was going to be Disney Land.

* * *

Kendall never knew time could fly so fast. He felt like they had just arrived, yet they were home again. It had been an insanely long day at Disney Land. They have tried everything they could. After that, they went to a fancy restaurant where they had, as Katie said "the most delicious chocolate cake in the universe". Finally, they hung out at the pool for a bit, but they quickly decided to return to the apartment. While Katie still had a bit of energy left, the guys felt exhausted after this super long day.

Kendall was the last one to get in the shower. Before he did, he turned to his little sister.

"I'm coming in ten minutes to tuck you in."

Katie smiled and Kendall watched her walk to her room with a grin. There was one more "present" waiting for Katie today, and as much as Kendall could tell, she was suspecting nothing.

Ten minutes later, fresh out of the shower and dressed in his PJs, Kendall shoved the envelope into his pocket and went up to Katie's door, knocking quietly.

"Come in!" She called.

Kendall smiled and stepped in, closing the door behind him. Katie was sitting on her bed in her rope and PJs. As Kendall sat next to her, Katie went to lie under the covers, but was stopped by her brother.

"Not so fast, Baby Sister." He smiled. Katie frowned at him. "You still have one last gift to recieve."

Katie's eyes lit up as she quickly hugged him, bouncing excitedly.

"What is it?"

Kendall chuckled as he pulled the envelope out of his pocket and gave it to his little sister.

"Read it."

Katie immediately ripped the envelope open. Her excitement turned into curiousity as she recognised her old handwriting. What could this possibly be?

Kendall watched as Katie read the letter, supressing a smile. He wondered if he would have to chase her or not.

Katie read the letter over and over again. She had a faint memory about writing the vow. The day has come. She's eleven and she doesn't have a boyfriend. Which means...

Without thinking, Katie jumped up from her bed and bolted for the door.

Kendall laughed as he ran after the little girl. It wasn't long before he caught up to her, and threw her over his shoulder. Smiling slyly, he slowly headed back to her room.

"Nooo, Kendall!" Katie shrieked through her giggles, squirming in her brother's grip. "Don't! No!"

Kendall held her tight as he opened Katie's bedroom door again, chuckling at her protests.

"What's wrong, Baby Sis?" He laughed, carrying her to the bed.

"Don't do it!" Katie begged, laughing even harder as Kendall sat down and gently laid her over his knee.. "Nooo!"

Kendall chuckled too as he placed a hand on the small of her back, keeping her securely in place and lifted the back of her rope, revealing her pajama-clad bottom.

"NOOO!" His little sister's hands flew back to protect her backside, the little girl still shaking with laughter. She let out another squeak as Kendall took her wrists and gently pinned them against her back. He then lifted his hand, chuckling evilly.

"One, two, three, four..." Katie shrieked with laughter as spank after spank rained down on her bottom. She could tell Kendall wasn't using much force since the slaps barely stung. Still, she continued to squirm, giggling loudly.

"... Nine, ten, eleven." Kendall counted through his own laughter, then raised his hand a bit higher in the air. "Aaand... One to grow on!"

Katie laughed histerically as a slightly more forceful spank landed.

"Ow!" She giggled as Kendall let her up. She rubbed her backside a bit before punching Kendall in the shoulder.

"I hate you!" She laughed. Kendall scooped her up, hugging her tight.

"I love you." He chuckled, kissing her forehead repeatedly. Katie snuggled into his embrace, laughing along with him.

"I still hate you."

After the laughter died down, Kendall gently lifted her off his lap and pulled back the covers. Katie yawned as she climbed in.

"Are you sleepy?" Kendall asked as he tucked her in tight. Katie smiled lightly and nodded.

"Alright. Goodnight, birthday girl." He whispered, kissing her forehead again. "I love you."

Katie watched her brother leave.

"I love you too."

Kendall turned off the lights before exiting. Katie continued smiling to herself. Best birthday ever.


End file.
